Virulence characteristics of male genital tract Escherichia coli isolated from semen of suspected infertile men

An experimental study to decipher the implications of antigenic sharing between Proteus mirabilis and mouse spermatozoa in eliciting an antisperm immune response: A potential culprit in immune infertility

The present study aims to investigate the antigenic cross reactivity between the receptor from Proteus mirabilis and spermatozoa against a common sperm immobilization factor, SIF, by calorimetric and competitive inhibition studies, and the immunogenicity of this receptor to evoke the formation of antisperm antibodies and their subsequent role in fertility outcome. The sperm binding receptor from Proteus mirabilis (PM-SBR) was extracted from ultrasonicated cell debris by treating it for 12 h at 37°C with 1 M NaCl. After being purified by gel permeation chromatography, its molecular weight as determined by SDS-PAGE was observed to be ≈ 47 kDa. The detrimental impacts of Sperm immobilizing factor (SIF) on spermatozoa viz. motility, viability, and morphology were mitigated when SIF was preincubated with various concentrations of PM-SBR. Using isothermal titration calorimetry, the entropy of the SIF-PM-SBR interaction was found to be -18.31 kJ/mol, whereas the free energy was 28.4 J/mol K. FTIR analysis was used to evaluate the binding interactions between PM-SBR and SIF. In addition, mice that were administered antibodies against PM-SBR were unable to conceive, in contrast to mice that were administered Phosphate buffer saline (PBS) or pre-immunization serum as controls. In light of this, we may conclude that anti-PM-SBR antibodies act as anti-sperm antibodies. Our work found that molecular mimicry between Proteus mirabilis and spermatozoa may cause antisperm immune reactivity. As a result of an immunological response to PM-SBR, infected individuals may produce antibodies against an epitope similar to one found on spermatozoa which helps in developing new strategies for managing autoimmune responses and infertility.

Bacteriospermia - A formidable player in male subfertility

Bacterial colonization of male reproductive tissues, cells, and fluids, and the subsequent impact of bacteria on the sperm architecture, activity, and fertilizing potential, has recently gained increased attention from the medical and scientific community. Current evidence strongly emphasizes the fact that the presence of bacteria in semen may have dire consequences on the resulting male fertility. Nevertheless, the molecular basis underlying bacteriospermia-associated suboptimal semen quality is sophisticated, multifactorial, and still needs further understanding. Bacterial adhesion and subsequent sperm agglutination and immobilization represent the most direct pathway of sperm-bacterial interactions. Furthermore, the release of bacterial toxins and leukocytic infiltration, associated with a massive outburst of reactive oxygen species, have been repeatedly associated with sperm dysfunction in bacteria-infested semen. This review serves as a summary of the present knowledge on bacteriospermia-associated male subfertility. Furthermore, we strived to outline the currently available methods for assessing bacterial profiles in semen and to outline the most promising strategies for the prevention and/or management of bacteriospermia in practice.

Role of Lactobacillus in Female Infertility Via Modulating Sperm Agglutination and Immobilization

Infertility has become a common problem in recent decades. The pathogenesis of infertility is variable, but microbiological factors account for a large proportion of it. Dysbiosis of vaginal microbiota is reportedly associated with female infertility, but the influence of normal vaginal microbiota on infertility is unclear. In this review, we summarize the physiological characteristics of the vaginal tract and vaginal microbiota communities. We mainly focus on the bacterial adherence of vaginal Lactobacillus species. Given that the adherent effect plays a crucial role in the colonization of bacteria, we hypothesize that the adherent effect of vaginal Lactobacillus may also influence the fertility of the host. We also analyze the agglutination and immobilization effects of other bacteria, especially Escherichia coli, on ejaculated spermatozoa, and speculate on the possible effects of normal vaginal microbiota on female fertility.

Contraceptive efficacy of sperm agglutinating factor from Staphylococcus warneri, isolated from the cervix of a woman with inexplicable infertility

BACKGROUND

Voluntary control of fertility is of paramount importance to the modern society. But since the contraceptive methods available for women have their limitations such as urinary tract infections, allergies, cervical erosion and discomfort, a desperate need exists to develop safe methods. Vaginal contraceptives may be the answer to this problem, as these are the oldest ways of fertility regulation, practiced over the centuries. With minimal systemic involvement, these are also the safest. Natural substances blocking or impairing the sperm motility offer as valuable non-cytotoxic vaginal contraceptives. Antimicrobial peptides (AMPs) isolated from plants, animals and microorganisms are known to possess sperm immobilizing and spermicidal properties. Following this, in the quest for alternative means, we have cloned, over expressed and purified the recombinant sperm agglutinating factor (SAF) from Staphylococcus warneri, isolated from the cervix of a woman with unexplained infertility.

METHODS

Genomic library of Staphylococcus warneri was generated in Escherichia coli using pSMART vector and screened for sperm agglutinating factor (SAF). The insert in sperm agglutinating transformant was sequenced and was found to express ribonucleotide-diphosphate reductase-α sub unit. The ORF was sub-cloned in pET28a vector, expressed and purified. The effect of rSAF on motility, viability, morphology, Mg⁺⁺-dependent ATPase activity and acrosome status of human sperms was analyzed in vitro and contraceptive efficacy was evaluated in vivo in female BALB/c mice.

RESULTS

The 80 kDa rSAF showed complete sperm agglutination, inhibited its Mg²⁺-ATPase activity, caused premature sperm acrosomal loss in vitro and mimicked the pattern in vivo showing 100% contraception in BALB/c mice resulting in prevention of pregnancy. The FITC labeled SAF was found to bind the entire surface of spermatozoa. Vaginal application and oral administration of rSAF to mice for 14 successive days did not demonstrate any significant change in vaginal cell morphology, organ weight and tissue histology of reproductive and non-reproductive organs and had no negative impact in the dermal and penile irritation tests.

CONCLUSION

The Sperm Agglutinating Factor from Staphylococcus warneri, natural microflora of human cervix, showed extensive potential to be employed as a safe vaginal contraceptive.

Contraceptive Sperm Agglutinating Proteins Identified in Staphylococcus warneri, Natural Microflora of an Infertile Woman

Staphylococcus warneri, isolated from the cervix of an adult female with unexplained infertility, was found to agglutinate human spermatozoa in vitro leading to their death. A genomic library of S. warneri was generated using pSMART-Escherichia coli vector-host system. Approximately 3500 transformants were screened and four showed sperm agglutinating activity. Sperm agglutinating proteins (SAPs) were partially purified from the positive transformants and were found to agglutinate sperms in vitro. Cloned ORFs in positive transformants were sequenced and ORF finder identified them as endonuclease, accessory secretory protein-Asp1, accessory secretory protein-Asp2 and signal transduction protein. Mannose was found to competitively inhibit sperm agglutination, indicating that SAPs in S. warneri bind to mannose in glycoprotein receptors on the surface of sperms for agglutination. This is the first report on identification of SAPs which may be responsible for unexplained infertility in women and may be used as contraceptive agents.

[Effect of semen bacterial infection on semen parameters and analysis of drug resistance in 74376 male infertility patients]

OBJECTIVE

To investigate the effect of semen bacterial infection on semen parameters in male infertility patients and analyze of the drug resistance profile of the bacterial isolates.

METHODS

According to the results of bacterial culture, the semen samples of 74376 infertile men collected between April, 2016 and April, 2017 were divided into infection group and non-infection group, and the infertility type and semen parameters were compared between the two groups. The bacterial species and the drug sensitivity of the isolates were analyzed.

RESULTS

Bacterial infections were detected in 1.38% of the total semen samples collected. The positivity rate of semen bacterial infection was 1.41% in normal semen group, 1.55% in asthenospermia group, 1.18% in oligospermia group, 1.57% in asthenospermia/ oligospermia group, and 0.17% in azoospermia group. The positivity rate was lower in azoospermia group than in the other groups. Bacterial infection mainly affected sperm motility (P < 0.05), sperm density and forward motile sperm ratio (P < 0.01). The most common bacterial species causing the infections included, in the descending order of frequencies, Escherichia coli (63.59%), Klebsiella pneumoniae subspecies (19.80%) and Proteus mirabilis (13.22%). Drug susceptibility tests showed that the isolates of Escherichiacoli, Pneumonia Klebsiella pneumonia subspecies and Citrobacter koseri were commonly resistant to amoxicillin; Pseudomonas aeruginosa isolates were resistant to Bactrim and ampicillin/sulbactam; Staphylococcus aureus isolates were resistant to penicillin.

CONCLUSIONS

Male infertile patients have a low bacterial infection rate in the semen. Bacterial infection severely affects the sperm fertilization process by causing impairment of sperm motility and lowered sperm density. Escherichia coli is the most common pathogenic bacterium for the semen infection. With the exception of Staphylococcus aureus, the other bacterial strains isolated were found to be sensitive to imipenem and meropenem.

Lipopolysaccharide Compromises Human Sperm Function by Reducing Intracellular cAMP

A worldwide decline in the quality of human semen is currently occurring. In mammals, sperm are produced from diploid stem-cell spermatogonia by spermatogenesis in testes and become mature in epididymis. Nevertheless, these biological processes can be affected by Gram-negative bacterial infection mediated by lipopolysaccharide (LPS), the major endotoxin of Gram-negative bacteria. It is well known that LPS can disturb spermatogenesis and affect sperm maturation and quality in vivo. However, the effect of LPS on the ejaculated mature sperm in vitro remains unclear. Thus, this study aimed to assess the in vitro toxicity of LPS on human sperm function and to elucidate the underlying mechanism. Human sperm were incubated with LPS (0.1-100 μg/ml) for 1-12 h in vitro and, subsequently, sperm viability, motility and capacitation, and the acrosome reaction were examined. LPS dose-dependently inhibited total and progressive motility and the ability to move through a viscous medium of the sperm but did not affect sperm viability, capacitation, and the acrosome reaction. To explore the underlying mechanism of LPS's actions, we examined the effects of LPS on the intracellular concentrations of cyclic adenosine monophosphate (cAMP) and calcium ([Ca(2+)]i) and protein-tyrosine phosphorylation of human sperm, which are key regulators of human sperm function. LPS decreased intracellular cAMP dose-dependently but had no effect on [Ca(2+)]i and protein-tyrosine phosphorylation of human sperm. These findings suggest that LPS inhibits human sperm motility by decreasing intracellular cAMP.

Immunocontraceptives: new approaches to fertility control

The rapidly increasing global population has bowed the attention of family planning and associated reproductive health programmes in the direction of providing a safe and reliable method which can be used to limit family size. The world population is estimated to exceed a phenomenal 10 billion by the year 2050 A.D., thus presenting a real jeopardy of overpopulation with severe implications for the future. Despite the availability of contraceptive methods, there are over one million elective abortions globally each year due to unintended pregnancies, having devastating impact on reproductive health of women worldwide. This highlights the need for the development of newer and improved contraceptive methods. A novel contraceptive approach that is gaining substantial attention is "immunocontraception" targeting gamete production, gamete outcome, or gamete function. Amongst these, use of sperm antigens (gamete function) seems to be an exciting and feasible approach. However, the variability of immune response and time lag to attain titer among vaccinated individuals after active immunization has highlighted the potential relevance of preformed antibodies in this league. This review is an attempt to analyze the current status and progress of immunocontraceptive approaches with respect to their establishment as a future fertility control agent.

Isolation of a spermatozoal immobilization factor from Staphylococcus aureus filtrates

Staphylococcus aureus isolated from the cervix of an infertile woman was found to cause complete immobilization of human spermatozoa in vitro. Only the cell culture and cell-free supernatant showed immobilization activity, indicating that the sperm immobilization factor might be released extracellularly by the organism because no activity was observed with the washed cells. Heat treatment of the supernatant at 60 °C for 10 min waived its immobilizing activity, indicating that the active component may be a protein. The bioactive molecule from the supernatant was purified to homogeneity by ammonium sulfate precipitation, gel permeation chromatography, and ion exchange chromatography. Sperm immobilization factor (SIF) was found to be an ~20 kDa protein. SIF at a concentration of 10 µg/mL was required to cause 100% immobilization of human spermatozoa after 30 min of incubation at 37 °C, whereas a concentration of 150 µg/mL caused immediate immobilization, and a concentration of 200 µg/mL resulted in instant loss of viability of human spermatozoa, observed by eosin–nigrosin staining. Scanning electron microscopy showed that the treatment of human spermatozoa with SIF caused multiple defects in the head, midpiece, neck, and tail region of human spermatozoa.

Influence of enterococci on human sperm membrane in vitro

AIM

To study the influence of enterococci on human sperm membrane in vitro.

METHODS

Ejaculated human sperm were artificially infected with beta-hemolytic or non-beta-hemolytic enterococci at the bacteria: sperm ratio of 50:1 at 37 degrees . Sperm membrane integrity was examined after incubation for 1, 3 and 5 h by hypoosmotic swelling (HOS) test and electron microscopy.

RESULTS

Sperm infected with beta-hemolytic enterococci had lower HOS scores compared with non-beta-hemolytic strains or uninfected control (P < 0.01). The HOS test scores of sperm infected with beta-hemolytic enterococci increased in the presence of phosphatidylcholine, an inhibitor of hemolysin. Non-beta-hemolytic strains showed no significant difference in swelling rate, compared with the control group (P > 0.05). It was shown by electron microscopy that beta-hemolytic enterococci caused significant rupture of human sperm membrane.

CONCLUSION

Beta-hemolytic enterococci caused human sperm membrane injury, and might be mediated by the hemolysin of enterococci.

Bacterial infection and semen quality

We have analyzed two infertile male cohorts with (n=39) and without genital tract infection (n=14) comparing their selected seminological parameters with healthy controls (n=30). Genital tract infection (GTI) has been defined by the presence of leukocytes and pathological bacterial strains identified with Bio-Merieux tests. We have found statistically significant deteriorated semen volume, sperm concentration, motility, morphology and vitality in ejaculated samples of patients with genital tract infection in comparison to healthy controls. Statistically significant negative influence towards sperm reproductive potential has been revealed in case of Escherichia coli, Ureaplasma urealyticum and Staphylococcus aureus.

Bacteria induce expression of apoptosis in human spermatozoa

An increased number of sperm undergoing apoptosis has been observed during inflammatory processes in the male genital tract, which might be associated with elevated reactive oxygen species (ROS) levels. However, another factor to stimulate apoptosis could be the direct contact with bacteria or its products, even in the absence of ROS. The aim of this study was to investigate whether bacteria can directly initiate apoptosis in human spermatozoa. Human spermatozoa selected by density gradient centrifugation were incubated with polymorphonuclear granulocytes (PMN) isolated from blood and/or E. faecalis, E. coli or S. aureus. As ROS inductor in PMN, phorbol-12-myristate-13-acetate was used. After incubating the cells for 60 min at 37 degrees C, ROS were determined by chemiluminescence and phosphatidyl serine (PS) externalization was analyzed by flow cytometry with Annexin V-FITC and propidium iodide (PI). The increase in the percentage of spermatozoa Annexin V-FITC-positive/ PI-negative (early event of late apoptosis) was significant after the incubation with PMN plus PMA, PMN plus E. coli and E. coli alone. The percentage of spermatozoa Annexin V-FITC-positive/ PI-positive (apoptosis/necrosis) increased significantly in sperm incubated with E. coli and S. aureus (20.3% +/- 3 and 13.6% +/- 3.2 compared to sperm alone, 6% +/- 0.5). Sperm incubated with PMN-PMA activated showed only a relative increase in apoptosis/necrosis (8.4% +/- 1). Our results show that bacteria directly increase the PS externalisation in ejaculated human sperm. This way of inducing apoptosis does not require external ROS and may result from anyone of the molecular mechanisms that account for changes in motility, vitality and DNA integrity, that are characteristics of spermatozoa in male genital tract infection.

Testicular sperm aspiration and intracytoplasmic sperm injection for persistent infection of the ejaculate

OBJECTIVE

To report the successful use of testicular sperm aspiration and intracytoplasmic sperm injection in the presence of an Escherichia coli-infected ejaculate that previously caused repeated embryo degeneration.

DESIGN

Case report.

SETTING

University medical center.

PATIENT(S)

A 38-year-old woman who did not conceive for 6 years with repeated IVF attempts. Escherichia coli was isolated from both the oocyte culture dish and her male partner's ejaculate.

INTERVENTION(S)

Testicular sperm aspiration and intracytoplasmic sperm injection followed by ET.

MAIN OUTCOME MEASURE(S)

Clinical outcome.

RESULT(S)

Establishment of a pregnancy delivered at term.

CONCLUSION(S)

Patients undergoing IVF treatment who have repeated embryo degeneration caused by bacterial infection originating in the ejaculate may be treated successfully with testicular sperm aspiration and intracytoplasmic sperm injection.

Influence of urogenital infections on sperm functions

Many studies have examined the impact of genital tract infections on male fertility; however, the effect of bacteriospermia on sperm quality is still controversial. Bacterial infections are more frequently found in semen samples from asymptomatic infertile patients than in those from fertile men. Bacteriospermia is also a common problem of male partners from couples undergoing IVF. Therefore, the effects of microorganisms on human sperm acrosome reaction of oocytes have been studied in vitro and in vivo. Incubation of spermatozoa with Escherichia coli or Mycoplasma hominis in vitro resulted in reduced sperm motility and inducibility of acrosome reaction (delta AR) after exposure to calcium ionophore A23187. To show possible effects of E. coli and mycoplasma species on sperm functions in vivo, data from 488 patients were evaluated, in whose ejaculates microbiological examinations and determinations of acrosome reaction after exposure to low temperature had been performed. U. urealyticum and E. coli were found in semen samples from 52 and 31 men, respectively. M. hominis was only present in a minor number of samples and was not included in this study. Semen concentrations of E. coli and U. urealyticum ranged between 500-100,000 cfu x ml-1 and 100-80,000 cfu x ml-1. No correlation was found between delta AR and concentration of bacteria (Spearman rank correlation coefficient, E. coli: r-0.081, P = 0.6644; U. urealyticum: r = -0.081, P = 0.5698). In 69% of cases with U. urealyticum infection and reduced inducibility of acrosome reaction, this sperm function was normal after antibiotic therapy. However, improvement of acrosomal function may only be due to intra-individual variations of acrosome reaction. While E. coli and mycoplasma species affect sperm functions in vitro, the present data and a review of the literature fail to demonstrate similar effects in vivo.

Microbiology of semen specimens from males attending a fertility clinic

The relationship between semen quality, pyospermia and bacteriology was studied in 201 semen specimens from male patients attending a fertility clinic. Semen quality parameters were within normal limits in 115 (57%) patients, slightly reduced in 60 (30%), and 26 (13%) had findings indicating reduced fertility. Twelve patients (6%) had pyospermia. In 182 patients, 552 microorganisms were detected, including Enterobacteriaceae (2.8%), Gardnerella vaginalis (9.6%), Chlamydia trachomatis (1.6%), Mycoplasma genitalium (0.9%), and Ureaplasma urealyticum (11.8%). Semen quality was neither related to occurrence of microorganisms nor pyospermia. However, pyospermia was associated with simultaneous growth of Gardnerella vaginalis and Ureaplasma urealyticum. The exact nature of this association could not be ascertained, in as far as the males were not questioned about urethritis symptoms.

In vitro effect of Escherichia coli on human sperm acrosome reaction

Escherichia coli are known to reduce human sperm motility. The purpose of the present study was to examine whether these bacteria may also affect the acrosome reaction, which is another important sperm function. The acrosome reaction was determined in spermatozoa from 29 fertile men by triple stain after 3-h incubation at 37 degrees C with 2 x 10(6) E. coli/mL or without bacteria (control). Each sample was treated with 0.1% DMSO (spontaneous acrosome reaction) or calcium ionophore A23187 (induced acrosome reaction) for 1 h at 37 degrees C. The inducibility of the acrosome reaction was significantly lower in semen samples pretreated with E. coli than in the control samples (9.8 +/- 4.2% vs. 12.7 +/- 5.3%; p < .05). The results demonstrate that E. coli affect the inducibility of the acrosome reaction in vitro and may impair the fertilizing capacity of human spermatozoa.

Adherence of Escherichia coli to sperm: a mannose mediated phenomenon leading to agglutination of sperm and E. coli

OBJECTIVE

To investigate the mechanism of adherence between Escherichia coli and sperm.

DESIGN

Experimental study performed with donor sperm and male genital tract-derived E. coli.

SETTING

Andrology unit of a university hospital.

PATIENTS

None.

INTERVENTIONS

Monitoring of sperm-E. coli agglutination; addition of sugars to block adherence; electron microscopy.

MAIN OUTCOME MEASURE

Sperm-E. coli agglutination.

RESULTS

Escherichia coli readily adhered to and agglutinated sperm. The phenomenon was observed at E. coli to sperm ratios as low as 1:20; maximum sperm agglutination involving approximately 90% of spermatozoa was seen with ratios of 1:5 or higher. By transmission electron microscopy, E. coli adherence was observed both on sperm heads and tails. Heteroagglutination could be blocked by D-mannose and alpha-methyl-mannopyranoside but not by other sugars. Preincubation of sperm or E. coli with mannose resulted in block of agglutination, indicating mannose-binding structures both on sperm and E. coli.

CONCLUSIONS

Adherence of E. coli to sperm is mediated by mannose and mannose-binding structures present on both cell types. Agglutination of sperm by E. coli may be relevant in male and female infertility.